1. Field of the Invention
The present invention relates to a slider used for a flying magnetic head or the like and a method for manufacturing the same.
2. Description of the Related Art
A flying magnetic head used in a magnetic disc apparatus or the like is configured by forming a thin film magnetic head element at the rear end of a slider. In general, a slider includes rail portions whose surfaces act as flying surfaces (air bearing surfaces) and includes a taper or step portion in an air inflow portion (in the vicinity of the end at the air inflow side) such that the rail portions slightly fly above the surface of a magnetic recording medium such as a magnetic disc by a stream of air flowing in through the tapered or stepped surface.
In general, a slider having a taper portion at an air inflow portion is formed into a predetermined configuration through a mechanical process such as lapping. A slider having a step portion at an air inflow portion thereof (hereinafter referred to as "a step leading type slider") is formed into a predetermined configuration through an etching process utilizing photolithography, for example, as disclosed in Japanese examined patent publication (KOKOKU) No. H5-8488.
A step leading type slider can be accurately formed even into a complicated configuration because it is manufactured using photolithography instead of a mechanical process as described above. This is advantageous in that it facilitates control over flying characteristics and in that processing cost can be reduced.
Recently, a need has arisen for a reduction in the flying amount of a slider for an improved recording density. It is also desired to improve the stability of the flying of a slider in order to achieve access at a higher speed. Negative pressure sliders have been put in use to satisfy such needs. In general, a negative pressure slider is formed with a negative pressure generating portion having a concave configuration to generate a negative pressure between two rail portions. Such a negative pressure slider has a microscopic configuration on a surface thereof facing a recording medium and, especially, the height of the rail portions is significantly smaller than those in conventional sliders.
Such a negative pressure slider of the above-described step leading type, the depths of the step portion and negative pressure generating portion relative to the flying surfaces are different from each other.
A description will now be made with reference to FIG. 12 through FIG. 21 on an example of a method for manufacturing a step leading type negative pressure slider of the related art and on problems with the related-art methods for manufacturing sliders.
It is assumed here that a slider 211 having a configuration as shown in the plan view of FIG. 13 is manufactured. The slider 211 includes two rail portions 212 whose surfaces serve as flying surfaces 212a, a step portion 213 formed at an air inflow portion and a negative pressure generating portion 214 formed to extend from the central portion to the air outflow side thereof. For example, the depth of the step portion 213 relative to the flying surfaces 212a is 1 .mu.m, and the depth of the negative pressure generating portion 214 relative to the flying surfaces 212a is 3 .mu.m. The slider 211 includes a thin film magnetic head element 215 provided in a position close to the end at the air outflow side of one of the rail portions 212.
According to the manufacturing method in the related art, the slider bar including a plurality of thin film magnetic head elements arranged in a row is first secured to a jig after lapping of the surfaces thereof to serve as flying surfaces is completed.
The subsequent steps will be described according to the flow chart shown in FIG. 12. First, as shown in FIGS. 14 and 15, a photoresist mask 231 is formed using photolithography on regions 222 of the slider bar 210 to become the rail portions 212 (step S201). FIG. 14 is a plan view showing a region of the slider bar 210 which is to become one slider, and FIG. 15 is an enlarged sectional view taken along the line 15--15 in FIG. 14.
Next, for example, ion milling is performed to etch a region 223 to become the step portion 213 and a region 224 to become the negative pressure generating portion 214 by, for example, 1 .mu.m using the photoresist mask 231 (step S202).
Next, as shown in FIGS. 16 and 17, the photoresist mask 231 is removed (step S203). FIG. 16 is a plan view similar to FIG. 14, and FIG. 17 is a sectional view similar to FIG. 15.
Next, as shown in FIGS. 18 and 19, a new photoresist mask 232 is formed on the regions 222 to become the rail portions 212 and the region 223 to become the step portion 213 using photolithography (step S204). FIG. 18 is a plan view similar to FIG. 14, and FIG. 19 is a sectional view similar to FIG. 15. Next, for example, ion milling is performed to etch the region 224 to become the negative pressure generating portion 214 by, for example, 2 .mu.m using the photoresist mask 232 (step S205).
Next, the photoresist mask 232 is removed as shown in FIGS. 20 and 21 (step S206). The slider 211 is thus formed. FIG. 20 is a plan view similar to FIG. 14, and FIG. 21 is a sectional view similar to FIG. 15.
According to the method for manufacturing a slider of the related art as mentioned above, to form the step portion 213 and negative pressure generating portion 214 which are different in depth from each other relative to the flying surface 212a, the series of steps of forming photoresist masks, etching and removing the photoresist mask is repeated twice. Therefore, when the second photoresist mask 232 is formed, the photoresist mask 232 must be positioned accurately especially at the boundaries between the regions 222 to become the rail portions 212 and the region 224 to become the negative pressure generating portion 214.
In practice, however, when the second photoresist mask 232 is formed, it is subjected to a positional shift, for example, in the range from 0.3 to 0.5 .mu.m attributable to low positioning accuracy of an exposure mask for photolithography and the like as shown in FIGS. 18 and 19.
As a result, steps 241 are formed on side surfaces connecting the flying surfaces 212a and negative pressure generating portion 214 as shown in FIGS. 20 and 21. When such steps 241 is formed, the flying characteristics of the slider 211 will be different from design values, which can cause problems such as a horizontal shift of the slider in use in some cases.